The field of this invention relates to a method of manufacture for producing an article of jewelry made from precious metal and one or more gems and a tool for creating the seats for the gems in the wax model.
Gem setting directly into precious metal has long been known to be expensive and a time consuming process. Efforts have been made to mass produce articles of jewelry with using the lost wax process and eliminating the need for setting gems directly into an article of precious metal.
U.S. Pat. No. 4,392,289 issued on Jul. 12, 1983 to Michaud provided for a molding technique for jewelry where a rubber mold is formed to produce a wax model with a seat formed by molded grooves. The diamond or other gem such as a ruby or sapphire is then set in the grooves. An investment material surrounds the wax model and gem in preparation of making a cast about the gem via the lost wax process. The investment forms a hardened shell about the model and gems and the wax is melted and drained. The gem remains in position and retained by the surrounding investment. Molten precious metal is then cast into the formed cavity where the wax model use to be. After the molten metal is allowed to solidify, the article of jewelry is then devested, with the sprues and gates removed. The article is then ready to be polished. The gem is mounted in the precious metal in the same position as it was in the wax model. Gems such as diamonds, rubies and sapphires are not harmed by the heat commonly used in the lost wax and casting process.
This method has seen commercial success and many different types of jewelry from rings to pendants have used this casting method. However, this method has several disadvantages and complexities. Firstly, because the vertical position and the depth of the molded grooves are preset in the rubber mold and thus also preset in the wax model, great care must be used to find diamonds and other gems that are sized to fit the preset grooves. In theory, the above process succeeds if all the gems are within the design manufacturing tolerances for the molded wax model. In other words, with the known mold with the preset molded grooves, the gems must be sized to fit the wax model.
However, in practicality, one usually has certain available gems which must be fitted into a wax model. If one has a several gems of different sizes, the wax model made with preset uniform grooves is incompatible for use with the existing gems. In other words, it is desired that the wax model accommodates the existing or desired gems. This accommodation is particularly desirable when a piece of jewelry has multiple gem stones and each gem stone is sized slightly different. It is preferable that the top of all the gem stones be level in many types of popular channel designs. However, it is expensive to form a rubber mold for each set of pre-existing gems with a preset molded groove. One would end up with many rubber molds for each model of jewelry.
It is desirable to have a rubber mold form a wax model without the preset grooves and then have the wax mechanically removed by a tool that precisely locates each groove for each gem stone such that the gems are precisely positioned to present aligned upper facets. After the grooves are then formed, the lost wax method of casting gold or other precious metal with the gems may then proceed.
What is needed is a tool that allows this method of mechanically removing wax to form the grooves for seating gems.
In accordance with one aspect of the invention, a method of manufacturing an article of jewelry includes the steps of forming a wax model having opposing retaining walls that form a channel for seating a gem therein. The wax model has a certain degree of resiliency enabling flexing of the retaining walls to allow entry of a gem into the channel. Mechanical removal of the wax material occurs to form opposing grooves in the channel. Preferably, the wax is cut away to form the opposing grooves in the opposing retaining walls of the formed wax model. The grooves engage a girdle of a gem below a distal edge of the retaining walls. The gem is snapped into the channel to allow the girdle to enter into engagement into the seating grooves. A hard investment mold is formed about the gem and wax model. The lost wax process is then used to replace the wax model with cast precious metal within the investment mold. The investment mold is then devested from the formed article of jewelry with the set gem mounted thereto.
Preferably, a cutting tool is used to cut the groove, the groove has side walls angled to follow the contour of the girdle of the gem.
It is also desirable to slide a positioning ledge of the tool along the distal edge of the retaining wall and have a blade distal blade section of the tool cut into said retaining wall below the distal edge to form the grooves. In one embodiment, the tool slides a sufficient distance to cut a groove sufficiently long to seat a plurality of gem stones in a row.
In accordance with another aspect of the invention, a tool is used for forming an undercut groove seat in a wax model for retaining a gem stone in place on the wax model. The tool comprises a handle section a bit with a ledge, a recess leg section, and blade section. The bit extends from the handle. The ledge section is smooth and preferably with smooth rounded edges for sliding on a distal end of a retaining wall. The recess leg portion extends below the ledge portion. A side extending blade portion is at a distal section of the leg for cutting the wax away and to form an undercut groove spaced below the distal end of the retaining wall.
Preferably, the side extending blade portion is tapered with canted cutting edges that conforms to the contour of a girdle portion of a gem. It is also preferable that the ledge is substantially flat to promote a orthogonal seating of the tool on the distal end of the retaining wall. The ledge has rounded edges to prevent the ledge from cutting into the distal end of the retaining wall. In one embodiment, the ledge has an extended portion from the bit portion interposed between the handle and the ledge.